Lamp masking method and apparatus

ABSTRACT

A motor vehicle lamp assembly having a light source for emitting light and a source enclosure having a light transmissive portion for transmitting light from the light source to an illumination zone. The enclosure is affixed with a material which covers a selected region of the light transmissive portion of the enclosure. The material is electrically energized to alter an amount of light transmitted from the light source to the illumination zone. A drive circuit electrically coupled to the material energizes the material to control a light output from the lamp assembly.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] The present application is a continuation in part containingcommon subject matter with presently pending U.S. patent applicationSer. No. 10/108,827, filed Mar. 27, 2002, now U.S. Pat. No. 6,550,943which is a continuation-in-art of U.S. patent application Ser. No.09/967,437 which was filed in the United States Patent and TrademarkOffice on Sep. 28, 2001 which is a continuation in part of U.S. patentapplication Ser. No. 09/865,402 which was filed in the United StatesPatent and Trademark Office on May 25, 2001, now U.S. Pat. No.6,491,416, and which is entitled “Headlamp Masking Method andApparatus.” The subject matter of the co-pending application and issuedU.S. Patent are hereby incorporated by reference.

FIELD OF THE INVENTION

[0002] The present invention concerns a vehicle lamp having a controlfor selectively rendering portions of the lamp light transmissive undervehicle operator control.

BACKGROUND ART

[0003] All motor vehicles include a control for switching between highbeam and low beam operation of the motor vehicle headlamps. This controlmay be implemented by a floor mounted switch but most typically in morerecent designed motor vehicles is implemented with a stalk on thevehicle steering column that is easily actuated by a motor vehicleoperator.

[0004] When the high beam option is selected, the vehicle headlamps arefocused in a direction that illuminates further in advance of thevehicle to improve a motorist's ability to see details in his or herline of sight. When an oncoming vehicle approaches, the motorist canswitch to low beam operation to avoid temporarily blinding the oncomingdriver. Fog lamps are occasionally installed on vehicles to direct alamp output downward in a direction closer to the vehicle to enable themotorist to more clearly see during rain and foggy conditions.

[0005] Vehicle head lamps most typically contain two separate lightbulbs that can be independently activated. When one of the bulbs isactivated, a low beam lamp output is produced and when a second bulb ofthe two bulbs is activated a high beam lamp output is provided. In the1980's when headlamps having halogen light bulbs were first built, thegovernment enacted photometric tests. These tests dictated that light ofa high enough intensity to cause spot blindness in other motorists didnot reach certain regions in a space in front of a motor vehicleheadlamp. Spot blindness was only a problem for halogen lights sincethese lights produce a much more intense output when compared withnon-halogen lamps.

[0006] U.S. Pat. No. 5,517,389 to Meyers concerns an electrochromic lampassembly including a reflector having two or more reflective surfaces. Alight source and an electrochromic means is positioned between the lightsource and at least one reflective surface. Each reflective surfacedirects light in a different direction. The electrochromic means iscapable of blocking light from exiting the lamp assembly from at leastone direction.

SUMMARY OF THE INVENTION

[0007] The present invention concerns a lamp assembly or, preferably,for use with a motor vehicle. The lamp assembly includes regions on alight transmitting portion of an assembly enclosure that can beselectively controlled to change from opaque to highly transmissive. Theenclosure can be formed as a separate unit such as a housing or formedintegral with other portions of the motor vehicle. In the exemplaryembodiment, the enclosure is a housing. If used as a headlamp, the lampassembly can operate as a fog lamp, can provide a low beam output lamp,can provide a high beam output lamp and can provide various combinationsof these lamp operations. Other vehicle lamps such as a tail lamp canutilize features of the invention to control both the appearance andfunction of such lamps.

[0008] One exemplary embodiment of a lamp assembly constructed inaccordance with the invention includes a light source, preferably a lampbulb, for emitting light from the lamp assembly that is supported by anenclosure having a light transmissive portion for transmitting lightfrom the lamp bulb to an illumination zone. At least a portion of theenclosure is affixed with a material which covers a selected region ofthe light transmissive portion of the enclosure. By electricallyenergizing the material, its light transmissive properties arecontrolled, thereby controlling an amount of light transmitted from thelight source to the illumination zone. A drive circuit is electricallycoupled to the material.

[0009] When used as a headlamp, the exemplary embodiment of theinvention gives a motorist direct control of intensity and zones ofillumination. The motorist can adjust the illumination intensity andzone for specific traveling conditions, i.e. weather, terrain, time ofday etc. This creates a safer environment to operate the motor vehicle.

[0010] Practice of the exemplary embodiment of the invention is achievedwith one, high intensity light source supported by a headlamp assemblyhaving a reflective region for directing light through the lighttransmissive portion of the assembly. This structure can provide highbeam, low beam and fog lamp outputs from a headlamp without resort tomultiple bulbs and bulb housings.

[0011] An exemplary embodiment of the invention includes multipleregions that are defined by the material. These photometric patcheseliminate a need for a bulb shield. Current commercially available bulbshields are made specifically for a high beam, low beam or fog lamp bulbhousing. Alternatively, the bulb shield must be mechanicallyrepositioned inside a bulb housing. Either of these two techniques ismore complex and costly than a headlamp assembly built in accordancewith the present invention.

[0012] The material can be any material where when electricallyenergized alters the light emitted from the light source to theillumination zone. Preferably, the material is a PDLC material (polymerdispersed liquid crystal) which scatters light rather than absorbing thelight to block its transmission. This characteristic greatly reducesheat build up associated with masking a halogen lamp, whose highintensity light output causes a rapid build up of heat in any materialwhich absorbs that light. The material can be affixed to the enclosurein any suitable manner apparent to these of ordinary skill in the art inview of this disclosure. In the exemplary embodiment, the enclosure iscoated with the material.

[0013] In one exemplary embodiment of the present invention, when thebulb is extinguished, a current is applied to all regions of the PDLCmaterial thereby causing those regions to be light transmissive forcosmetic purposes. An alternative option is to apply current to the PDLCmaterial only when the bulb is illuminated. This would serve a cosmeticpurpose so that a headlamp, tail lamp, fog light etc. could be renderedopaque when not illuminated and rendered light transmissive in acontrolled manner across it surface when its associated lamp or bulb ison. As a still additional option, the PDLC regions can be rendered lighttransmitting when the motor vehicle engine is running regardless of thebulb condition so that a parked vehicle will have an opaque lampassembly.

[0014] These and other objects, advantages and features of the inventionwill become better understood from a detailed description of anexemplary embodiment of the invention which is described in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 is a perspective view of a headlamp assembly constructed inaccordance with the present invention;

[0016]FIGS. 2A, 2B and 2C are front plan, side plan, and section viewsof a headlamp housing that forms part of the FIG. 1 assembly;

[0017]FIG. 3 is a schematic depiction of a drive circuit for activatingcontrol components of the headlamp assembly depicted in FIG. 1

[0018]FIG. 4 is a first alternate depiction of a headlamp assemblyconstructed in accordance with the invention

[0019]FIG. 5 is a second alternate depiction of a headlamp assemblyconstructed in accordance with the invention;

[0020]FIG. 6 is a third alternate depiction of a headlamp assemblyconstructed in accordance with the invention;

[0021]FIG. 7 is a depiction of a tail lamp assembly constructed inaccordance with the present invention;

[0022]FIG. 8 is a schematic depiction of a headlamp assembly including alens cap for increasing a spacing of light transmitting control materialfrom a light emitting bulb; and

[0023]FIGS. 9A and 9B illustrate alternate arrangements for supportinglight transmitting control material.

EXEMPLARY EMBODIMENT FOR PRACTICING THE INVENTION

[0024] Turning now to the drawings, FIG. 1 illustrates a headlampassembly 10 that includes a headlamp bulb 12 for emitting light mountedto a bulb housing 14 having a light transmissive portion or lens 16 foremitting light from the headlamp bulb 12 to an illumination zone infront of the headlamp assembly 10. An interior surface 20 of the 10light bulb housing 14 reflects light reaching the surface 20 back intothe housing interior so that it will exit the housing through the lighttransmissive portion 16. The bulb 12 can take the form of a traditionalhead lamp bulb or can be constructed from other known light sources.Some of such light sources include, for example, High IntensityDischarge (HID), Halogen, Flouorescent, Incandescent, and High IntesityLight emitting diode/diodes.

[0025] The light transmissive portion of the housing is coated atspecified regions with a coating material. When these regions areelectrically energized the coating material is rendered more lighttransmissive to alter the amount of light transmitted from the bulb tothe illumination zone. A drive circuit 30 (see FIG. 3) electricallycoupled to the regions of coating material energizes the coatingmaterial and thereby control a light output from the headlamp assembly.

[0026] In accordance with the exemplary embodiment of the invention thelight transmissive portion of the housing is coated with three bands 32,34, 36 of the coating material. These bands are independently energizedto adjust the light output from the headlamp assembly 10. The headlampassembly 10 is for a motor vehicle. The opacity of the three bands 32,34, 36 of coating material are selectively controlled to adjust theopacity of the three bands thereby producing a high beam output, a lowbeam output and a fog lamp output, respectively, from the headlampassembly 10. In addition to the three bands 32, 34, 36, the disclosedembodiment of the invention includes a plurality of smaller regions 50of coating material that are coupled to the drive circuit 30 by means ofconductors 52 routed across the light transmissive portion of thehousing. Both the bands 32, 34, 36 and additional smaller regions orpatches 50 are most preferably built using cut to size sheets of apolymer dispersed liquid crystal material, known as PDLC material. Oneexample of a commercially available PDLC material is Polymer StabilizedTechnology (PST) available from Kent State Liquid Crystal Institute atKent State University, POB 5190, Kent, Ohio 44242. Another commerciallyavailable material is SPD film from Research Frontiers Incorporated,having a business address of 240 Crossways Park Drive, Woodbury, N.Y.11797. In addition, PDLC material is available from Polytronix, Inc.,having a business address of 805 Alpha Drive, Richardson, Tex. 75081 andthe Liquid Crystal Institute at Kent State University, POB 5190, Kent,Ohio 44242. This sheet of material can be cut to an appropriate shapeand applied to the light transmissive portion of the bulb housing.

[0027] The coating material may be affixed to the inside of the lens 16with a translucent adhesive to protect the material from weathering thatwould occur outside the lens 16. The coating material may also beapplied to an outer surface of the lens 16 using a protective laminate.Additionally the coating material may be a prefabricated panel, which isthen clipped or locked into place when the headlamp assembly housing isconstructed.

[0028] The patches 50 are solely for photometric purposes and are notunder direct control of the motorist. The patches are rendered opaque atany time that the headlamp bulb 12 is outputting light to create a fieldof illumination which is in accordance with governmental photometricstandards. The patches 50 are made translucent or light transmitting byapplying a current to the patches only when the headlamp bulb 12 is notproducing light.

[0029] In the disclosed exemplary embodiment, the adhesive used toattach the PDLC material to the lens 16 is an electrically conductiveadhesive. Use of the conductive adhesive avoids the use of metal on thesides of the patches 50 and allows wiring to connect to the adhesivethat is applied along the outer edges of the PDLC material. This use ofadhesive enhances the cosmetics of the lens 16 as well as eliminatingthe cost of edging the PDLC with copper or other conductive material.One suitable conductive adhesive is sold under the designation NOELLE805-19 System, a two component (A+B) high performance, silver filled,room temperature curing adhesive that is available from NoelleIndustries, Adhesives, Coatings and Conductives, 83 Alexander Rd. Unit 3Billerica Mass. 01821.

[0030] In an alternative mounting scheme, the lens 16 has a multiplelayer construction. As seen in FIG. 9A a piece of PDLC material 60 issandwiched between inner and an outer layers 16 a, 16 b of lighttransmitting plastic. In this alternate embodiment energizing leads orwires 62 are routed to Indium Tin Oxide layers on inner and outersurfaces of the PDLC material through a narrow gap between the inner andouter layers 16 a, 16 b of the lens 16. This multiplayer embodimentdefines distinct regions of PDLC material but in a way wherein thoseregions are defined at the time the lens 16 is fabricated rather than ata subsequent time by applying PDLC regions to the lens by means of anadhesive. In an alternate embodiment shown in FIG. 9B a single lens 16houses the bulb 12 and individual segments 70 of coating material areconstructed by sandwiching a suitably sized and shaped PDLC material 71between inner and outer layers 72, 74 of plastic. The resulting regionsof coating material are then attached to the lens 16 using theconductive adhesive 76. As a modification to this design, the regions ofcoating material can be attached to the lens 16 by means of mechanicalattaching hardware such as for example by means of clips that hold anarray of such segments together as well as clips that attach the arrayto an outer surface of the lens 16.

[0031] Drive Circuit 30

[0032] Referring now to FIG. 3, the drive circuit 30 includes a userinterface that includes a switch selector 100 for controlling inputs 102a, 102 b, 102 c to a programmable controller 110. The programmablecontrol includes a control program operating system that responds to thesignals on the inputs 102 a, 102 b, 102 c to produce on a set ofcontroller outputs 112 a-112 f. A driver circuit 114 is coupled to thecoating material to apply a pulse width modulated signal to the coatingmaterial for altering the light transmissive characteristics of saidcoating material. In accordance with the disclosed exemplary embodimentof the invention, the highest light transmission occurs when the band isactivated with a large alternating current square wave signal.

[0033] In accordance with the disclosed embodiment of the invention,there are three bands 32, 34, 36 of coating material. Each band isindependently controlled by the controller 110. Thus, by referring toFIG. 3, one sees that the band 32 is coupled to two conductors 120 a,120 b, the band 34 is coupled to the two conductors 122 a, 122 b, theband 36 is coupled to the two conductors 124 a, 124 b. The lighttransmitting status of the other smaller regions 50 are controller by anoutput 112 f so that the controller activates each of these regions toachieve approximately the same amount of light transmission. Inaccordance with the preferred embodiment of the invention, the bands 32,34, 36 each overlap with one or more of the additional small regions orpatches 50.

[0034] Current is applied to the PDLC patches 50 when the headlamp bulb12 is not emitting light. This provides an appearance of a clearheadlamp lens. At any time the headlamp bulb 12 is producing light allthe regions 50 are deprived of current so as to be in an opaque state.This prevents light from the bulb 12 from reaching photometric testspoints located in front of the patches.

[0035] The programmable controller is programmed so that when one of thebands is driven to a state wherein the material that makes up that bandis highly light transmissive, its associated smaller regions of materialare in a state of low transmission, i.e. they are highly opaque.Consider the topmost band 32 in FIG. 1. This band 32 is covered inselected regions or zones by three additional smaller regions or patches50 a, 50 b, 50 c. When the band 32 is activated by the controller 110 tobe highly light transmissive, the regions or patches 50 a, 50 b, 50 care not activated or energized, and consequently, are opaque. Since allpatches are coupled to the same output from the controller 110 controlsall the patches, when the patches 50 a, 50 b, 50 c are opaque, thepatches applied to overlap other bands of the lens are also opaque.

[0036] The switch 100 has three contacts 100 a, 100 b, 100 c so that 23or eight different control signal states can be generated as indicatedin Table 1 that follows. As described below, the controller 110 also maybe programmed to adjust the light transmitted from the lamp assembly torespond to whether the engine is running or the headlamps are turned onby the motorist. These inputs are referred to as ‘control inputs’ in theschematic depiction of FIG. 3. TABLE 1 Control Signal States Lights OffCurrent applied to all bands High Beam On Current applied to band 32,none on 34, 36 Low Beam On Current applied to band 34, none on 32, 36Fog Beam On Current applied to band 36, none on 32, 34 Low Beam with FogCurrent applied to band 34, 36, not 32 High Beam with Fog Currentapplied to band 32, 36, not 34 Low Beam with High Beam Current appliedto bands 32, 34, not 36 Low Beam, High Beam and Fog Current applied toall bands

[0037] It is a requirement of the exemplary embodiment of the presentinvention that when the bulb 12 is extinguished, a current is applied toall three bands 32, 34, 36. This renders the PDLC material of the bands32, 34, 36 light transmissive for cosmetic purposes. Automotivecompanies spend much money on headlamp design every year to createcosmetically attractive bulb shields and practice of the invention helpsin achieving an attractive appearance. An alternative option is to applycurrent to the PDLC bands only when the bulb 12 is illuminated. Thiswould serve a cosmetic purpose so that a headlamp, taillamp, fog lightcould be rendered opaque when not illuminated and rendered lighttransmissive in a controlled manner across its surface when itsassociated lamp is on. As a still additional option, the PDLC regionscan be rendered translucent when the motor vehicle is running regardlessof the bulb condition.

[0038] So long as the controller 110 is powered up by a signal derivedfrom the twelve volt signal from the motor vehicle battery, thecontroller 110 provides pulsed on/off signals at the two outputs 112 a,112 b. These signals have a frequency of about 64 hertz and have a dutycycle of 50%. These pulses pass through high current inverter drivers130 to a step up transformer 132. The step up transformer 132 has acenter tap 134 coupled to the twelve volt output from the vehiclebattery. The transformer produces an alternating square wave signalacross two bus conductors 140, 142 that alternates back and forthbetween +40 volts and 40 volts at a frequency of 64 hertz.

[0039] As stated above, the programmable controller 110 also producessignals at outputs 112 c, 112 d, 112 e, 112 f for controlling a lighttransmissive characteristic of the bands 32, 34, 36 and collectively theregions 50. These outputs from the controller 110 are 128 hertz, pulsewidth modulated, square waves. The width of the pulse determines thelight intensity from the bulb 12 transmitted by an associated controlelement of coating material. Each of the outputs 112 c, 112 d, 112 e,112 f is coupled to an associated optoisolator 150 a, 150 b, 150 c, 150d through an inverting, high current drive amplifier 152. Consider theoutput 112 c. When this output goes high, the inverter produces a lowsignal which turns on a light emitter of the optoisolator 150 a. This inturn turns on a transistor of the optoisolator 150 a, therebytransmitting the pulse to a bridge rectifier 160. The bridge rectifieracts as a valve to transmit the 64 hertz signal across the busconductors 140, 142 across an associated control element.

[0040] The pulse width of the 128 hertz signal at the outputs 112 c, 112d, 112 e, 112 f determines the light intensity of the light transmittingportions of the housing. The pulse width controls the on time of abridge rectifier by switching the associate optocoupler on and off. Thisin turn determines a length of time that the 64 hertz signal from thetransformer is applied to an associate PDLC coating member. A resistor162 (10k) and a capacitor 164 (1 microfarad) determining the rate atwhich the voltage can rise across the PDLC. Given more time (widerpulse), the voltage will go higher and increase the light intensitytransmitted through an associated control element such as one of thebands 32, 34, 36. Given less time (narrow pulse), the voltage will belower and decrease the light intensity. The controller can control thepulse width in increments of 30 microseconds (.000030 seconds) providinggood resolution on light intensity control. In one exemplary embodiment,however, the coating material is either rendered essentially transparentdue to application of the +/−40 volt signals from the transformer or isrendered opaque by blocking all signals from the transformer. The highlytransparent state for the band 32, for example, is achieved byapplication of a constant high output signal at the output 112 c fromthe controller 110. In accordance with alternate procedures, a dimmingof the light transmission is achieved through pulse width modulating anoutput from the controller 110 with a controlled pulse width signal.Using the programming capability of the controller 110 it is possible tocontrol a level of opacity of each individual PDLC band in order tooptimize the headlamp assembly performance. The operating system of thecontroller 110 can be programmed with preset levels of opacity basedupon the type of beam selected. For example, if may be that the optimum“low beam with fog” lamp combination emits a preferred amount of lightby making the low beam PDLC band 34 20% opaque. This value can beprogrammed or adjusted depending on the configuration of the lampassembly and is generally an empirically determined factor. It may alsobe possible to use a master dimming switch that controls the opacity ofthe three PDLC bands 32, 34, 36. Note, in this regard, the opacity ofthe patches 50 is constant so the dimming capacity noted above does notapply to these regions. An alternate method of energization uses acontrol over a Direct Current voltage level rather than a pulsing oralternating signal. In this embodiment the Direct Current applied to aPDLC region is varied to adjust the opacity of the PDLC region.

[0041] The bulb housing 14 is most preferably made from a front, lighttransmissive portion 16 that functions as a lens and an interior lightreflecting surface 20. A rear wall 16 of the assembly 10 supports thebulb 12 in relation to the front, light transmissive portion so thatwhen the bulb is energized to emit light those portions of the lighttransmissive portion 170 not blocked by sheets of opaque PDLC materialtransmit light to an illumination zone or region. Both the lighttransmissive and reflector sections 16, 20 are molded plastic parts.During assembly, the bulb 12 is mounted to the reflector section 20 andconductors for energizing the PDLC regions are attached to thereflector. The PDLC regions are attached to the light transmissiveportion 16 of the housing. In the disclosed embodiment of the invention,the bands 32, 34, 36 are supported on an inner surface of the lighttransmissive section 16. The PDLC areas 50 are attached to an outersurface of the light transmissive section 16. The reflector section 20most preferably has associated to it a material that enhances the lightreflecting capacity of an inner surface of the section 20.

[0042] The programmable controller 110 most preferably is amicroprocessor that receives a DC energization signal from a voltageregulator circuit (not shown) powered by a motor vehicle battery. Themicroprocessor is programmed with an operating system that periodicallysenses the status of the input switches and provides appropriate pulsewidth modulated outputs from the outputs 112 a-112 f. The use of amicroprocessor adds flexibility to a manner in which the PDLC coatedregions are activated. In certain instances such flexibility is notneeded and a programmed logic array could be used to provide the inputsensing and output signal control.

[0043] In the exemplary embodiment of the invention, there is no benefitto separate programming of the PDLC patches 50 for different activationsof the three PDLC bands 32, 34, 36. However, the photometrics of avehicle's headlamp depend upon the shape, height and overall dimensionsof the car as well as the shape of the bulb housing's reflective surfacewhich is dependent on each vehicle's front end design. Therefore, ifsome photometric points in front of the headlamp are necessary for ahigh beam but not a low beam, and if these points were affected by thelow beam when it is operated without the high beam, the controller 110can be programmed to only make the photometric point opaque in the highbeam state by selective activation of the patches depending on the highbeam/low beam status.

[0044] Photometric standards pursuant to 49 C.F.R. sec 571.108(b) aretabulated below and indicate zones of coverage for the PDLC patches 50.TABLE 2 Photometric Test Point Values for Mechanical Aim HeadlightingSystems UPPER BEAM Test Points Candela Candela (degrees) Maximum Minimum2U-V — 1,500 1U-3L and 3R — 5,000 H-V 75,000 40,000 H-3L and 3R — 15,000H-6L and 6R — 5,000 H-9L and 9R — 3,000 H-12L and 12R — 1,500 1.5D-V —5,000 1.5D-9L and 9R — 2,000 2.5D-V — 2,500 2.5D-12L and 12R — 1,0004D-V 12,000 —

[0045] TABLE 3 Photometric Test Point Values for Mechanical AimHeadlighting Systems LOWER BEAM Test Points Candela Candela (degrees)Maximum Minimum 10U-90U 125 — 4U-8L and 8R — 64 2U-4L — 135 1.5U-1R to3R — 200 1.5U-1R to R 1,400 — 1U-1.5L to L 700 — 0.5U-1.5L to L 1,000 —0.5U-1R to 3R 2,700 500 H-4L — 135 H-8L — 64 0.5D-10.5L to L 3,000 —0.5D-1.5R 20,000 10,000 1D-6L — 1,000 1.5D-2R — 15,000 1.5D-9L and 9R —1,000 2D-15L and 15R — 850 4D-4R 12,500 —

[0046] TABLE 4 Photometric Test Point Values for Visual/Optical AimHeadlighting Systems UPPER BEAM Test Points Candela Candela (degrees)maximum Minimum 2U-V — 1,500 1U-3L and 3R — 5,000 H-V 75,000 40,000 H-3Land 3R — 15,000 H-6L and 6R — 5,000 H-9L and 9R — 3,000 H-12L and 12R —1,500 1.5D-V — 5,000 1.5D-9L and 9R — 2,000 2.5D-V — 2,500 2.5D-12L and12R — 1,000 4D-V 12,000 —

[0047] TABLE 5 Photometric Test Point Values for Visual/Optical AimHeadlighting Systems LOWER BEAM Test Points Cendela Candela (degrees)maximum Minimum 10U-90U 125 — 4U-8L and 8R — 64 2U-4L — 135 1.5U-1R to3R — 200 1.5U-1R to R 1,400 — 1U-1.5L to L 700 — 0.5U-1.5L to L 1,000 —0.5U-1R to 3R 2,700 500 H-4L — 135 H-8L — 64 0.6D-1.3R — 10,000 0.86D-V— 4,500 0.86D-3.5L 12,000 1,800 1.5D-2R — 15,000 2D-9L and 9R — 1,2502D-15L and 15R — 1,000 4D-4R 12,500 — 4D-20L and 20R — 300

[0048] FIGS. 4-6 depict alternate PDLC film coating patters for use withheadlamps constructed in accordance with the invention. In FIG. 4, thefront, forward facing light transmissive portion 16 of the housing iscoated with eight separate PDLC regions 210-217 which cover an entirefront surface of the housing 14. These regions 210-217 are independentlyenergized to adjust the light output from the headlamp assembly 10. Asseen in FIG. 4, four regions 210-213 cover the entire front lighttransmitting surface or lens with the exception of a ‘hole’ or centerregion 220 made up of four center regions 214-217. The hole 220 islocated at a region on the lens 16 at which the optics of the reflector20 (FIG. 2B) concentrates the field of light to a ‘hot spot’. By placingthe multiple regions 214-217 over the hot spot and individuallycontrolling their opacity, the shape and intensity of the light emittedthrough the hole 220 onto the road is controlled. Rendering the regions210-213 outside the hole 220 opaque eliminate any glare from side anglesto oncoming motorists.

[0049]FIG. 5 depicts the use of a multiple PDLC coating regions tocreate a grid 230 on the lens 16. This embodiment would give a greaterdegree of control of light being emitted from any region of the lens 16.As an example, if there is a horizontal cut-off above or below which nolight is to be emitted the segments of the grid above or below thatcutoff could be controlled to remain opaque and thereby prevent lightfrom being emitted through those regions. In either the FIG. 4 or theFIG. 5 embodiment of the invention, the programmable controller can beprogrammed to pulse a quadrant of the PDLC material on the bulb housingat a regular frequency so that it is rendered light opaque and thenlight transmissive with a fifty percent duty cycle. This pulsedoperation simulates a turn signal and would eliminate the need for aturning signal separate from the housing.

[0050]FIG. 6 depicts a third alternate array 232 of multiple regionsattached to a front surface of a lens 16. This embodiment includesmultiple bands of PDLC material that extend across the width of theheadlamp. One particular band 234 includes multiple smaller segments orregions of PDLC material to give a greater degree of control over thelight transmitting characteristics of the lens 16.

[0051] In certain bulb housing designs, the distance from the lightsource or bulb 12 to the lens 16 may be a short enough distance so thatthe lens temperature reaches or exceeds the operating limits of the PDLCfilm adhering to the lens. To deal with this potential problem thedistance between the bulb 12 and the PDLC regions can be extended by useof a cap 240 (FIG. 8) that fits over the front of the lens 16. An arrayof one or more selectively light transmitting PDLC regions 242 areapplied to an inner surface of a front light transmissive panel 244 ofsuch a cap 240. In this alternate embodiment (FIG. 8) the PDLC film isspaced from an outer surface of the lens by an air gap 246 that addsseparation between the bulb 12 and the PDLC materials supported by thecap 240. This added separation maintains the temperature of the PDLCmaterials within safe operational temperatures. Air circulation in theregion of the PDLC materials is achieved by venting through a pluralityof slots 248 along a side of the cap 240.

[0052]FIG. 7 illustrates an alternative use of the present invention.This figure depicts a tail lamp 250 schematically showing both a brakelight 252 and a backup light 254. A taillarnp lens 260 faces outwardaway from a vehicle body. The lens supports an array 262 of one or morePDLC regions attached at selected locations across an inner surface.Wires 264 for selectively controlling the light transmissivecharacteristics of the array of PDLC regions are routed along an outsidesurface of the tail lamp 250 to a wiring harness 266 that activates thebrake and backup lights. Although the disclosed tail lamp 250 includesbrake and backup lights, a similar construction can be used with a taillamp having only a single tail light and as mentioned previously such alamp can include a control for simulating a turn signal rather thanturning on and off the bulb.

ALTERNATIVE EMBODIMENTS FOR PRACTICING THE INVENTION

[0053] In an alternative embodiment of the present invention, reversemode polymer dispersed liquid crystal is used as the coating material.Reverse mode PDLC material operates in a manner opposite to the PDLCmaterial disclosed in the exemplary embodiment. When current is appliedto the reverse mode PDLC material the material is rendered more opaque,on the other hand, when no current is applied, the material is renderedmore light transmissive.

[0054] As noted above, FIG. 1 illustrates a headlamp assembly 10 thatincludes a headlamp bulb 12 for emitting light that is mounted to a bulbhousing 14 having a light transmissive portion or lens 16 for emittinglight from the headlamp bulb 12 to an illumination zone in front of theheadlamp assembly 10. An interior surface 20 of the light bulb housing14 reflects light reaching the surface 20 back into the housing interiorso that it will exit the housing through the light transmissive portion16.

[0055] The light transmissive portion 16 of FIG. 1 is coated atspecified regions with a coating material. In the alternativeembodiment, when these regions are electrically energized the coatingmaterial is rendered more opaque to block more light from passingthrough the coating material, whereas when the regions are notelectrically energized, the coating material is more light transmissive.A drive circuit 30 (see FIG. 3) is electrically coupled to the regionsof coating material and thereby controls a light output from theheadlamp assembly.

[0056] Similar to the exemplary embodiment, in the alternativeembodiment of the invention the light transmissive portion of thehousing is coated with three bands 32, 34, 36 of the coating material.These bands are independently energized to adjust the light output fromthe headlamp assembly 10. The headlamp assembly 10 is for a motorvehicle. The opacity of the three bands 32, 34, 36 of coating materialare selectively controlled to adjust the opacity of the three bandsthereby producing a high beam output, a low beam output and a fog lampoutput, respectively, from the headlamp assembly 10. In addition to thethree bands 32, 34, 36, the disclosed alternative embodiment of theinvention includes a plurality of smaller regions 50 of coating materialthat are coupled to the drive circuit 30 by means of conductors 52routed across the light transmissive portion of the housing. Both thebands 32, 34, 36 and additional smaller regions or patches 50 are mostpreferably built using cut to size, sheets of a reverse mode polymerdispersed liquid crystal material. The coating material in thealternative embodiment may be affixed in a similar manner as disclosedin the exemplary embodiment.

[0057] The patches 50 are solely for photometric purposes and are notunder the direct control of the motorist. The patches are renderedopaque at any time that the headlamp bulb 12 is outputting light tocreate a field of illumination which is in accordance with governmentalphotometric standards. When the headlamp bulb 12 is not producing light,there is also no current being applied to the patches 50 so that thepatches are rendered light transmissive.

[0058]FIG. 3 shows the drive circuit 30 which includes a user interfacethat includes a switch selector 100 for controlling inputs 102 a, 102 b,102 c to a programmable controller 110. The programmable controlincludes a control program operating system that responds to the signalson the inputs 102 a, 102 b, 102 c to produce on a set of controlleroutputs 112 a-112 f. A driver circuit 114 is coupled to the coatingmaterial to apply a pulse width modulated signal to the coating materialfor altering the light transmissive characteristics of the coatingmaterial. In accordance with the disclosed alternative embodiment of theinvention, the highest light transmission occurs when the band is notactivated.

[0059] In accordance with one embodiment of the invention, there arethree bands 32, 34, 36 of coating material. The controller 110independently controls each band. Thus, by referring to FIG. 3, one seesthat the band 32 is coupled to two conductors 120 a, 120 b, the band 34is coupled to the two conductors 122 a, 122 b, the band 36 is coupled tothe two conductors 124 a, 124 b. The light transmitting status of theother smaller regions 50 are controlled by an output 112 f so that thecontroller regulates each of these regions to achieve approximately thesame amount of light transmission. In accordance with this embodiment ofthe invention, the bands 32, 34, 36 each overlap with one or more of theadditional small regions or patches 50.

[0060] No current is applied to the reverse mode PDLC patches 50 whenthe headlamp bulb 12 is not emitting light. This provides an appearanceof a clear headlamp lens. At any time the headlamp bulb 12 is producinglight, all the regions 50 are supplied current so as to render theregions more opaque. This prevents too high light levels from the bulb12 from reaching photometric tests points located in front of thepatches.

[0061] In accordance with the alternative embodiment, the programmablecontroller is programmed so that when one of the bands is unactivated,making the material highly light transmissive, its associated smallerpatch regions are activated to make them highly opaque. Consider thetopmost band 32 in FIG. 1. This band 32 is covered in selected regionsor zones by three additional smaller regions or patches 50 a, 50 b, 50c. When the band 32 is deprived of current by the controller 110 to behighly light transmissive, the regions or patches 50 a, 50 b, 50 c areactivated or energized, and consequently, are opaque. Since all patchesare coupled to the same output from the controller 110 controls all thepatches, when the patches 50 a, 50 b, 50 c are opaque, the patchesapplied to overlap other bands of the lens are also opaque.

[0062] The switch 100 has three contacts 100 a, 100 b, 100 c so that 2³or eight different control signal states can be generated. As describedbelow, the controller 110 also may be programmed to adjust the lighttransmitted from the lamp assembly to respond to whether the engine isrunning or the headlamps are turned on by the motorist. These inputs arereferred to as ‘control inputs’ in the schematic depiction of FIG. 3. Inthe alternative embodiment, the controller is programmed in a manner tocomport to the nature of the reverse mode PDLC material. Therefore, whenone of the bands 32, 34, 36 or patches 50 is to be rendered highly lighttransmissive, the controller does not supply current to these areas. Onthe other hand,when one of the bands or patches is to be opaque,according to the status of the switch, the controller supplies currentto this area. The same schematic depiction in FIG. 3, relating to theexemplary embodiment, applies to the disclosed alternative embodiment,however, the microprocessor outputs based on the control signals comingfrom the switch 100 are determined based on the nature of the reversemode PDLC material.

[0063] The alternative embodiment also contemplates that when the bulb12 is extinguished, current is not applied to all three bands 32, 34,36. This renders the reverse mode PDLC material of bands 32, 34, 36light transmissive for cosmetic purposes. The reverse mode PDLC materialallows the bands 32, 34, 36 to be light transmissive when the motorvehicle is not running. Since no current is applied to the reverse modePDLC material, use of this material eliminates the need for supplyingcurrent to the lamps when the motor vehicle is not running.

[0064] As noted above, the controller disclosed in the alternativeembodiment operates in the same manner as the controller disclosed inthe exemplary embodiment. The use of the reverse mode PDLC material inthe alternative embodiment requires current to render the bands 32, 34,36 and patches 50 opaque and no current to render these areas lighttransmissive. The microprocessor operating system determines whether ornot current is applied based on inputs from the switch 100 while allother aspects relating to FIG. 3 remain the same. A reverse mode PDLCmaterial that is clear in the undriven state and is opaque whenenergized is commercially available from Merck Liquid Crystals under thetrade designation Licrilite. (Registered Tradmark)

[0065] In another embodiment of the present invention, a dye isincorporated into the coating material that covers the lighttransmissive portion 16 of the light bulb housing 14 in the headlampassembly 10 of FIG. 1. Preferably, dichroic dye is added to the liquidcrystal coating material in order to provide color to the PDLC filmcovering the light transmissive portion 16 of the headlamp assembly 10.The dichroic dye can be incorporated into either the standard PDLCmaterial or the reverse mode PDLC material. In general, dichroic dyescomprise dye molecules that are generally a rod shaped configuration.These molecules align themselves parallel with the direction of theliquid crystal material and an electric field is applied to control thealignment of the dye molecules. In the presence or absence of anelectric field, the dye molecules can take on the appearance of beingeither colored or transparent. By altering the electric field, the dyemolecules can be converted from a transparent state to a colored stateand visa versa.

[0066] The type of dichroic dye can be selected to correspond to thetype of coating material being used, i.e. standard PDLC material orreverse mode PDLC material. In the case where the standard PDLC coatingmaterial is used, an absence of electric current renders the standardPDLC material more opaque. When a dye is incorporated into the standardPDLC material, the appearance in the absence of electric current isrendered more colored and opaque. The color will depend on the type andcolor of the dye selected. When electric current is applied to thestandard PDLC material, the material takes on a transparent appearance,thus allowing the transmission of light. Therefore, standard dyed PDLCmaterial will take on a more clear (non-colored) light transmissiveappearance or a colored light transmissive appearance.

[0067] With respect to reverse mode PDLC material, a dye is selectedthat is consistent with the physics of the reverse mode PDLC material.When no electric current is applied to the dyed reverse mode PDLCmaterial, the material takes on a more clear (non- colored) lighttransmissive appearance or a colored light transmissive appearance. Whenelectric current is applied to the dyed reverse mode PDLC material, thereverse mode material takes on a more colored opaque appearance. Forboth types of PDLC materials, the degree of color and/or opacity isproportional to the amount or absence of electric current being appliedto the material. Thus, the light transmissive portion 16 of the headlampassembly 10 in FIG. 1 can be rendered in different states of colorand/or opacity depending on different combinations of dye type, coatingtype and electric current.

[0068] Dyed PDLC material can be used in place of non-dyed PDLC materialin any of the preceding embodiments for the purpose of coloring aheadlamp, tail lamp, fog lamp, etc. The dye color can be selected toeither match or contrast the color of the vehicle for cosmetic purposes.In addition, dyes can be selected to provide for different colors oflight to be emitted from the light transmissive portion of the headlampassembly. Dichroic dyes can be incorporated into the PDLC material inany fashion known to those of skill in the art in view of thisdisclosure. The dyes normally are sold in powdered form and arecommercially available from Mistu Toatsu Senyro Company.

[0069] While the exemplary and alternative embodiments of the inventionhave been described with a degree of particularity, it is the intentthat the invention includes all modifications and alterations from thedisclosed design falling within the spirit or scope of the appendedclaims.

1. A lamp assembly comprising: a light source for emitting light fromthe lamp assembly; a light source enclosure having a light transmissiveportion for transmitting light from the light source to an illuminationzone, a portion of said enclosure including a material which covers aselected region of the light transmissive portion of the enclosure andwhich when electrically energized alters an amount of light transmittedfrom the light source to the illumination zone; and a drive circuitelectrically coupled to the material for selectively energizing thematerial and thereby controlling a light output from the lamp assembly.2. The apparatus of claim 1 wherein the material comprises a sheet ofpliable PDLC that is supported by the light transmissive portion of theenclosure.
 3. The apparatus of claim 1 wherein the light transmissiveportion of the enclosure has affixed to it multiple regions of thematerial that are independently energized to adjust the light outputfrom the lamp assembly.
 4. The apparatus of claim 1 wherein the multipleregions of the material form a matrix array of rows and columns that areindependently energized by the drive circuit to adjust the light outputfrom the lamp assembly.
 5. The apparatus of claim 1 wherein the lighttransmitting portion of the enclosure comprises inner and outer layersand wherein the material is supported between the inner and outer layersof said light transmitting portion.
 6. The apparatus of claim 5 whereinthe material comprises distinct regions that are individually energizedby conductors that are routed between the inner and the outer layers ofthe light transmitting portion of the enclosure.
 7. The apparatus ofclaim 6 wherein the material is a PDLC material.
 8. The apparatus ofclaim 1 wherein the material is supported by a separate enclosure capthat positions the material a spaced distance from the lighttransmitting portion of the enclosure to reduce heat transfer to thematerial from light source within said enclosure.
 9. The apparatus ofclaim 3 wherein the coating is affixed to the light transmitting portionof the enclosure with a conductive adhesive that forms a portion of aconductive path between the drive circuit and the material.
 10. Theapparatus of claim 3 wherein the driver circuit includes a userinterface for setting multiple inputs that control the lighttransmissive state of the multiple regions.
 11. The apparatus of 3wherein the driver circuit includes a programmable controller coupled toan output circuit that causes the multiple regions to exhibit one of twolight transmissive states, a relatively high light transmissive stateand a relatively low light transmissive state.
 12. The apparatus ofclaim 1 wherein the enclosure includes a light reflector and wherein alight transmissive portion of the enclosure includes an outer peripheralregion and a center region and wherein light reflected from a lightreflector is concentrated to exit the enclosure through said centerregion, said apparatus including one or more regions that cover theouter peripheral region of the light transmission portion of thehousing.
 13. The apparatus of claim 1 wherein the drive circuitcomprises: a) a user interface including a switch selector; b) aprogrammable controller for responding to the setting of the switchselector to produce a set of driver outputs; and c) a driver circuitcoupled to the material to apply an alternating signal to the materialto alter the light transmissive characteristics of said material. 14.The apparatus of claim 1 wherein the drive circuit includes a controloutput for adjusting a level of light transmission through a region ofsaid material depending upon an activation state of the light source.15. The apparatus of claim 1 wherein the drive circuit applies a directcurrent (DC) signal output for adjusting the light transmission level ofan associated region of said material.
 16. A lamp assembly comprising: alight source for emitting light from the lamp assembly; a enclosurehaving a light transmissive portion for transmitting light from thelight source to an illumination zone, a cap attached to the enclosurethat includes a light transmitting cap portion between the light sourceand the illumination zone which supports a material which whenelectrically energized alters an amount of light transmitted from thelight source to the illumination zone; said cap spacing the material adistance from the light source to control heat transfer from the lightsource to the material; and a drive circuit electrically coupled to thematerial for selectively energizing the material and thereby controllinga light output from the lamp assembly.
 17. A process for constructing alamp assembly comprising: positioning a light source within an enclosurehaving a light transmissive portion for transmitting light from thelight source to an illumination zone, mounting a material in relation tothe enclosure to cover selected regions of the light transmissiveportion; and coupling the material to a drive circuit for selectivelyenergizing the material which when electrically energized renders aregion of the light transmissive portion having the material more lighttransmissive to control light intensity transmitted from the lightsource to the illumination zone.
 18. The process of claim 17 wherein thematerial forms multiple regions in a matrix of rows and columns across asurface of said light transmissive portion of the lamp assembly whichare coupled to the drive circuit independently to allow independentcontrol over the light transmitting characteristics of said regionsduring operation of the headlamp assembly.
 19. The method of claim 17additionally comprising providing an interface for monitoring multipleinputs to control the light transmissive state of the material.
 20. Aprocess for operating a lamp comprising: positioning a light sourcewithin an enclosure having a light transmissive portion for transmittinglight from the light source to an illumination zone, affixing a materialin relation to the enclosure to cover selected regions of the lighttransmissive portion; coupling the material to a drive. circuit forcontrolling a light transmissive state of the material; and selectivelyactivating the drive circuit to energize the material and thereby rendera region of the light transmissive portion having the material morelight transmissive.
 21. The apparatus of claim 1 wherein the enclosureis a housing that can be coupled to a motor vehicle.